1. Field of the Invention
The present invention relates to a microchip useful as μ-TAS (Micro Total Analysis System) appropriately used for biochemical test of DNA, protein, cell, immunity and blood, chemical synthesis and environmental analysis, and in further detail, relates to a liquid reagent built-in type microchip having a liquid reagent for mixing with a sample intended for the test and the like built in the microchip previously.
2. Description of the Related Art
In recent years, the importance of sensing, detecting or quantifying biological materials such as DNA (Deoxyribo Nucleic Acid), enzyme, antigen, antibody, protein, virus and cell and chemical materials has increased in the fields of medical care, health, food and drug development, and various biochips and micro chemical chips (hereinafter named generically as microchips) capable of conveniently measuring them have been proposed.
The microchips generally have a fluid circuit inside thereof. In a liquid reagent built-in type microchip having a liquid reagent for treating a sample (such as blood) intended for the test and analysis or reacting with the sample built-in previously, the fluid circuit is mainly composed of, for example, each of a liquid reagent retaining portion to retain the liquid reagent, a measuring portion to measure the sample and the liquid reagent, a mixing portion to mix the sample and the liquid reagent and a detecting portion to analyze and/or test the mixed liquid as well as a minute flow path (for example, a width of approximately several hundred μm) for properly connecting each of these portions.
The microchip having such a fluid circuit has so many advantages that the sample and the reagent are slight in amount, the costs are inexpensive, the reaction rate is high, the high-throughput test may be performed and the test result may be immediately obtained at the site where the sample is gathered, as to be appropriately used for biochemical test such as a blood test, for the reason that a series of experiment and analysis processes performed in a laboratory may be performed in the chip of several centimeters square with a thickness of approximately several millimeters.
Here, in the liquid reagent built-in type microchip, when the liquid reagent sealed into the microchip decreases due to evaporation during the time from production to use of the microchip and the needed amount thereof is not secured at the time of use, the needed amount of the liquid reagent is not measured in the measuring portion, and mixing or reaction are not performed at an exact mixing ratio with the sample, so that the possibility is brought that precise test and analysis may not be performed.
For example, in Japanese Patent Laying-Open No. 2005-274199, as a method for restraining a slight amount of a specimen (a reagent or a sample) in a microchip from evaporating, a method for injecting a reagent and a sample into an internal flow path of a microchip to thereafter seal a flow path opening by injecting other liquid into the internal flow path is described, and the microchip applied to this method is described therein.
However, the microchip described in the above-mentioned Patent Document does not have a means for separating the liquid for sealing (sealing liquid) and the reagent, so that the above-mentioned method can not be directly applied to the microchip such that the reagent and the sample are each measured inside the microchip, and the measured reagent and the measured sample are mixed to perform precise test and analysis. That is to say, the sealing liquid can not be separated from the reagent, so that the reagent can not be exactly measured in the microchip, and thus mixing of the reagent and the sample at an exact mixing ratio, precise test and analysis can not be performed.